(a) Field of the Invention
The present invention relates to a LCD (liquid crystal display) device having a back light and, more particularly, to the structure of a reflecting plate for reflecting the back light from the rear side of the LCD panel toward the front side thereof.
(b) Description of the Related Art
A LCD device having a back light generally includes a reflecting plate at the rear side of the LCD panel, with a light-conductive sheet sandwiched between the LCD panel and the reflecting plate. The reflecting plate reflects the leakage light, which has passed through the rear surface of the light-conductive sheet, toward the front side of the LCD panel, thereby saving the light power resource. In general, the LCD panel, the light-conductive sheet and the reflecting plate have an equivalent size.
Patent Publication JP-A-4-371924 describes a structure shown in FIG. 1, wherein a printed circuit board 34 including a plurality of interconnect layers is disposed at the rear side of the LCD panel 13. The printed circuit board has a top surface covered by a uniform aluminum layer 21 which acts as a ground layer as well as a reflecting plate. A bezel 37 having a plurality of locking parts 20 is used for coupling the LCD panel 23 and the printed circuit board 34 together by adapting the bezel 37 at the front surface of the LCD panel 13. The LCD panel 13 and the printed circuit board 34 are electrically connected through flexible harnesses 19 for display of picture image. By using the uniform aluminum ground layer 21 of the printed circuit board 34 as a reflecting plate, the LCD device reduces the cost thereof by saving a dedicated reflecting plate.
In the conventional LCD device described in the publication, there are some drawbacks.
First, the size of the printed circuit board 34 is extremely large due to having a reflecting function for the back light of the LCD panel. The large size of the printed circuit board increases the total costs for the LCD device. More specifically, the cost for the printed circuit board generally depends on the number of printed circuit boards that can be obtained from a single board stuff having a fixed size.
Second, the LCD panel has irregularities in brightness of the screen. More specifically, the printed circuit board 34 generally mounts thereon a plurality of electric components such as a drive LSI for driving the LCD panel and a bypass capacitor used for a power source line for the LCD device. These electric components are generally attached onto one of the surfaces of the printed circuit board by using solder. This often generates a warped or wavy surface on the printed circuit board due to the heat generated in the soldering process. The warped or wavy surface hinders the reflecting surface of the printed circuit board from reflecting uniform light, whereby the LCD panel has the irregularities in brightness. In addition, it is usual that the electric components are mounted on the printed circuit board at the depressions of the printed circuit board which are formed for this purpose. The depressions, which hardly reflects light, also cause the irregularity or reduction in the brightness of the screen.
In view of the above, it is an object of the present invention to provide a LCD device having a reflecting plate which reflects uniform light to the LCD panel and has an additional function.
The present invention provides a LCD device including a LCD panel for displaying a picture image thereon, a light-conductive sheet disposed at a rear side of the LCD panel for conducting back light toward the LCD panel, a reflecting plate disposed at a rear side of the light-conductive sheet for reflecting the leakage back light passed through the rear surface of the light-conductive sheet, the reflecting plate having on a rear surface thereof a conductive film, and a combination of a tape carrier package (TCP) and a printed circuit board coupled to a periphery of the LCD panel, the TCP being electrically connected to the LCD panel for driving the LCD panel for display of the picture image based on signals transferred through the printed circuit board, the printed circuit board being disposed at a rear side of the LCD panel by folding the TCP toward the rear side of the LCD, the conductive film being disposed between the printed circuit board and the LCD panel.
In accordance with the LCD device of the present invention, the reflecting plate reflects the back light uniformly toward the LCD panel and, in addition, has a function for shielding the LCD panel against the noise generated by the printed circuit board. The reflecting panel having the conductive film only slightly raises the total costs for the LCD device, differently from the conventional LCD device having a large printed circuit board.
The above and other objects, features and advantages of the present invention will be more apparent from the following description, referring to the accompanying drawings.